Roland Ratzenberger's death runs to one minute and 16 seconds on YouTube. Viewed today, exactly 20 years later, as an exercise in grim foreboding it is hard to imagine how Alfred Hitchcock might have done it better.

A graphic in the bottom right-hand corner of the screen reads SENNA. The man with around 24 hours left to live sits in pole position at the 1994 San Marino Grand Prix. His is the time Michael Schumacher, Damon Hill and the rest are chasing down.

In bright tones, the commentators from Eurosport discuss the minor miracle of the previous day's practice, when Rubens Barrichello's car leapt clear of a metre-high safety barrier and crashed near full on into a fence, put there to prevent flying debris hitting the crowds.

Barrichello, a Brazilian like Senna, now a veteran racer but then a young man, was knocked unconscious. Quick medical intervention saved his life.

"Well, if that had happened in an aluminium car 10 or 15 years ago, the accident damage to the guys in them would have been far worse," cheerfully imparts David Price, the guest in the commentary box, and a leading figure in motor racing car design. "To see Rubens walking about this morning was a delight, really, after the level of the impact yesterday."

As Price says those words, Ratzenberger dies. He was 34, the same age as Senna. Except this was only his third Formula One grand prix, and he was contracted for just two more. An Austrian who had spent many years in the lower echelons of motor racing, his dream had taken the entirety of his youth to realise.

Ratzenberger during practice at Imola on 30 April 1994 (Getty)The camera cuts to a replay of his shattered Simtek car as it rolls slowly back out on to the track: "And Ratzenberger has had a heavy shunt indeed." The driver's head in its helmet is lolloping to one side. He was already dead. Perhaps a second before, a piece of broken-off bodywork trapped under his car had prevented it from turning, and he smacked into the wall at the Villeneuve Corner at 200 miles an hour, puncturing his skull, and dying instantly.

Ratzenberger was pronounced dead before he made it to the helicopter to be airlifted to Bologna's Maggiore Hospital, the same journey Senna would make the following day.

"We don't know what's gone on," is the last word from Eurosport's trackside voice, the body now removed, the half-obliterated vehicle being lifted off the track. "But in essence, the chassis of that car is intact. It's stood up to the impact extremely well."

Max Mosley, then president of the Fédération Internationale de l'Automobile, was one of the few figures in motor racing who went to Ratzenberger's funeral in Austria, instead of Senna's in Brazil.

"It was a small, sad, affair. A little bit more than a family thing," he said. "His partner was there, his parents, figures from Austrian motor racing.

"A lot of famous drivers were long-standing friends of Ayrton's so it's completely understandable they went to Ayrton's, but I just felt he was being neglected.

"Like all funerals, it was very, very sad. All you can really do is shake hands and express condolences, but there's no real conversation.

"I knew him quite well. The fact that he'd worked his way up, and got the job done, I admired. But he hadn't had a chance to enjoy any of the success yet. Ayrton had a short but amazing life. [Roland] had finally got there, but never had time to enjoy it."

Ayrton Senna, who would die the following day, talks to his friend Professor Sid Watkins after the Ratzenberger accident (Getty)It is tempting now to see that terrible weekend at Imola in northern Italy as a tragic boundary between two ages in Formula One. Death isn't part of the sport any more. In 1933 at Monza, three drivers died on a single day. In 1973, the death of the Frenchman François Cevert, in practice for the United States Grand Prix, scarcely cast a shadow over the victory celebrations.

In the 20 years since Imola, no one has died in a Formula One car. But no one had died in the 12 years leading up to it either, and there were already many claiming the sport had become "too safe".

"Up to then, most people said it's quite safe enough," said Mosley, "People were saying even then that it was too safe, that it had been sanitised."

The sport changed rapidly, not least in the introduction of Hans helmets, instantly recognisable now, that hold the head and neck firm, with cushioning around the shoulders.

Mosley admits that the changes that happened in the immediate aftermath of that weekend, "wouldn't have just happened anyway".

He also claims that the huge decline in deaths on the roads in Europe is in many ways down to improvements in technology and standards that were a direct consequence of changes made in the "panic" that followed Imola.

"Quiet and unassuming" are the words that have attached themselves to Ratzenberger in the years after his death. For Mosley, "That's a cliché, yes, but that is exactly what he was. Many of the best drivers are very insecure about their ability. That's what drives them on."

Certainly, Ratzenberger died doing what he loved, and he knew better than most the struggle it had been to get there. Twenty years on, the sport is in vigorous health and, in no small part thanks to both the lives that were lost that weekend, so are its drivers.